Method for a mobile terminal hand-off between a CDMA system and a WLAN

ABSTRACT

A method for handing over a mobile station from wireless local area network to CDMA 20001X system, comprises the following steps of: when a mobile station detects that a signal of wireless local area network is fading, determining to hand over to CDMA 20001X system; first, initiating a call in CDMA 2000 1X system; after a base station permits the terminal to access, establishing, by a packet control function node, a R-P connection with a packet data service node; establishing data transmission channel to CDMA 20001X system for the terminal by the packet data service node; performing data transmission between the terminal and the packet data service node via the packet control function node, and disconnecting, by the packet data service node, the R-P connection established between the packet data service node and wireless access point gateway in the wireless local area network system. The present invention uses the method of first establishing a new link and then disconnecting original link, in which the packet data service node does not change. The method realizes that the terminal can perform seamless handoff between CDMA 20001X system and wireless local area network, and can maintain data transmission uninterrupted.

TECHNICAL FIELD

The present invention relates to a method for handing over a mobilestation between two wireless systems, particularly, relates to a methodfor handing over a mobile station between CDMA20001X system and wirelesslocal area network (wireless LAN, referred as WLAN).

TECHNICAL BACKGROUND

CDMA (Code Division Multiple Access, referred as CDMA) technique is acommon multiple modulation technique based on wideband spread spectrumtechnology. CDMA 2000 1X system conforms to IS-2000 standard, which isin the first phase for the development of CDMA 2000 celluar mobilecommunication, and can provide transmission rate of 153.6 Kbps forpacket data.

FIG. 1 is the network schematic view for the combination of CDMA 2000 1Xsystem and wireless local area network, in which outside the block withdashed lines are function nodes of current CDMA 2000 1X system, andinside the block with dashed lines are function nodes added after acombination of CDMA 2000 1X system and wireless local area network. Inthe current CDMA 2000 1X system, base station transceivers 11 establishradio coverage area in an area to perform communication of mobilestations; base station controller 12 can control each base stationtransceiver; a packet control function node PCF generally is comprisedin the base station controller 12, which is used for forwarding messagebetween wireless subsystem and packet data service node PDSN 14; thepacket control function node PCF connects to base station controller 12via A8/A9 interface. Packet data service node PDSN 14 is an interfacefor CDMA 2000 1X system to access Internet, and an interface betweenpacket data service node PDSN 14 and packet control function node PCF 12is a standard R-P (Radio-Packet) interface, that is A10/A11 interface,in which A10 is data channel, and A11 is control channel. Packet dataservice node PDSN 14 provides access service for users of CDMA 2000 1X,and users perform authentication and accounting to the VisitedAuthentication Authorization Accounting server 19, Broker AuthenticationAuthorization Accounting server 17 and Home Authentication AuthorizationAccounting server 18 via PDSN 14.

When a user requests packet data service, firstly, it goes throughmobile switching center 13 to home location register HLR 20 where itsvalidity is authenticated; after the validity is authenticatedsuccessfully, A8/A9 interface is established between base stationcontroller BSC 12 and PCF 12, thereafter, PCF 12 transmits message toPDSN 14, and R-P interface is established between PCF 12 and PDSN 14.Then, PPP connection is established between mobile station and PDSN 14.After PPP connection is established successfully, if the user is asimple IP user, data service can start. If the user is a mobile IP user,MIP registration needs further perform, and, after MIP registration iscompleted successfully, the data service for mobile IP starts. When theuser accesses, it needs to perform a full PPP negotiation flow with PDSN14, in which PPP uses frame-making form of asynchronous HDLC.

Wireless local area network is the result of the combination forcomputer network and wireless communication technology, which supportscommunication between computers by using radio multiple access channel,and can provide the data transmission rate of up to 54 Mbps. Terminalsof wireless local area network generally dial by using point to pointprotocol over Ethernet (referred as PPPoE) or web+DHCP (Dynamic HostConfiguration Protocol).

Compared to wire network, wireless local area network WLAN hasadvantages of convenient installation, flexible usage, economy, and easyupdate, and, therefore, WLAN is used rapidly in the situation whereinternetworking in mobile and roaming between networks are needed,especially adapts to the situation where line distribution is not easyor data process is performed remotely; particularly in some fields, suchas exhibition, meeting, tour service, financial service and mobileoffice system, WLAN has very great chance for development. The characterof wireless local area network is low price, flexible networking,convenient installation, and supporting wireless data access with highspeed, which adapts to the application in hot pots such as airport,hotel, etc.

In wireless local area network, wireless terminal accesses fixedtelecommunication network via access point AP; AP provides user with thefunction of wireless access, provides access services of voice and data,and finishes the transfer of 802.11 and 802.3 protocol, in which thedata package after converted by AP is Ethernet data package. Butwireless local area network has limitation in authentication andaccounting mechanism for terminal access, it can only provideauthentication on physical transfer layer, but not provide accountingmechanism corresponding to terminal user, therefore, it can not meet theneed for applying on telecommunication level, and, moreover, thecoverage area of wireless local area network only limits to hot potareas, which results in very big limitation to the broad application ofwireless local area network.

After about 20 years development of CDMA system, CDMA 2000 1X system hasrecently also been used commercially in big scale. Not only itsauthentication and accounting mechanism is developed maturely and well,but also its coverage area is universally. But due to the widebandlimitation, the capability of CDMA 2000 1X system to provide terminaluser with high-speed access service is still limited now. Therefore, ifCDMA 2000 1X system and Wireless local area network system are combinedto an organic whole, they can exert their respective advantages fully,while the critical problem to combine two systems is how to realizeseamless handoff between two systems for terminal users. At present, notechnical document has been seen about handoff between two systems forterminal users.

SUMMARY OF INVENTION

The technical problem solved by present invention is to provide a methodfor handing over a mobile station between code division multiple accesssystem and wireless local area network, to realize seamless handoffbetween two systems for mobile stations.

In order to solve the above technical problem, the present inventionprovides a method for handing over a mobile station from wireless localarea network system to the CDMA 2000 1X system, which comprises thefollowing steps of:

Step 1, when a mobile station detects that a signal of wireless localarea network is fading or has disappeared, determining whether to handover the mobile station from wireless local area network to the CDMA2000 1X system, if yes, performing step 2; if not, continuously usingservice provided by original wireless local area network system ordisconnecting the connection;

Step 2, initiating call in the mobile station in CDMA 2000 1X system,after a base station permits the mobile station to access, establishingR-P connection with a packet data service node by a packet controlfunction node;

Step 3, after the packet data service node determines the mobile stationis a handoff user, establishing a data transmission channel in CDMA 20001X for the mobile station;

Step 4, performing data transmission between the mobile station and thepacket data service node via the packet control function node, anddisconnecting, by the packet data service node, the R-P connectionestablished between the packet data service node and wireless accesspoint gateway in wireless local area network system.

During handoff, if data transmission is needed between the packet dataservice node and the mobile station, the data is forwarded via wirelessaccess point gateway.

In the above step 3, the packet data service node directly uses the PPPconnection information of original link, and do not negotiate point topoint link again during handoff.

In order to solve the above technical problem, the present inventionfurther provides a method for handing over a mobile station from CDMA2000 1X system to a wireless local area network, which comprises thefollowing steps of:

Step 1, after detecting a signal of a wireless local area network in amobile station, connecting to an access point in the wireless local areanetwork, and determining whether to hand over the mobile station fromCDMA 2000 1X system to the wireless local area network system, if yes,performing step 2; otherwise, continuously using service provided byoriginal CDMA 2000 1X;

Step 2, performing dial connection to the wireless local area networksystem in the mobile station, and establishing connection with wirelessaccess point gateway;

Step 3, after the wireless access point gateway permitting the mobilestation to access, establishing a R-P connection between the wirelessaccess point gateway and a packet data service node;

Step 4, after the packet data service node determines the mobile stationis a handoff user, establishing a data transmission channel to thewireless local area network for the mobile station;

Step 5, performing data transmission between the mobile station and thepacket data service node via the wireless access point gateway, anddisconnecting, by the packet data service node, the R-P connectionestablished between the packet data service node and a packet controlfunction node in CDMA2000 1X system.

During said handoff, if data transmission is needed between the packetdata service node and the mobile station, data is forwarded via packetcontrol function node.

In the above step 2, the mobile station dials in PPPoE form.

In the above step 3, after the wireless access point gateway permits themobile station to access, it sends A11 registration request message tothe packet data service node; if the packet data service node receivesthe registration request message, it will returns A11 registrationanswer message to the wireless access point gateway; after the wirelessaccess point gateway receives the answer message, R-P connection isestablished successfully.

In the above step 4, the packet data service node directly uses PPPconnection information of original link.

From the above, during handoff, the handoff method of the presentinvention firstly establishes a new link, and thereafter disconnectsoriginal link; and in the process of handoff, the method maintains theoriginal packet data service node unchanged and without re-negotiationbetween the packet data service node and the mobile station for point topoint link, which can make the mobile station maintain data transmissionuninterrupted during handoff between CDMA 20001X system and wirelesslocal area network system, and can make the least signaling exchanged inthe process of handoff. The method provides data service for users byfully utilizing wide coverage, the character of CDMA 20001X system, andhigh speed data transmission, the character of wireless local areanetwork, moreover, realizing seamless handoff of terminal users betweenCDMA 20001X system and wireless local area network system, and realizingorganic combination of CDMA 20001X system and wireless local areanetwork system.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is the network configuration view for combination of CDMA 20001Xsystem and wireless local area network system;

FIG. 2 is the flow chart view for handing over a mobile station fromwireless local area network system to CDMA 20001X system according tothe present invention;

FIG. 3 is the flow chart view for handing over a mobile station fromCDMA 20001X system to wireless local area network system according tothe present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Next, the technical scheme of the present invention will be described indetails in conjunction with the drawings and embodiments.

The handoff method of the present invention adapts to a combinationnetwork of CDMA20001X system and a wireless local area network systemshown in FIG. 1. In FIG. 1, outside the block with dashed lines arefunction nodes of CDMA 20001X system, and inside the block with dashedlines are function nodes added after CDMA 20001X system combined with awireless local area network. In the Technical Background, the mainfunction nodes of CDMA 20001X system were explained; next, the mainfunction nodes related to the present invention will be explained.

Packet control function node PCF 12 mainly realizes connection of airwireless interface and packet data service node PDSN 14.

Packet data service node PDSN 14 is used to realize the access forterminal of CDMA 20001X system and wireless local area network system,and provides two kinds of access forms for terminal of CDMA 20001Xsystem and wireless local area network system: simple IP service andmobile IP service, and meanwhile maintains PPP connection informationfor the terminal; further, when a mobile station is handed over betweenthe wireless local area network system and CDMA 20001X system, packetdata service node PDSN 14 is further used to identify whether thecurrent user is a handoff user, that is, it judges whether the mobilestation requesting handoff has the ability to access CDMA 20001X systemand the wireless local area network system, if the current mobilestation is a handoff user, PDSN 14 opens the corresponding datatransmission channel for the current mobile station.

Access point (referred as AP) 16 is used to convert signal of thewireless local area network into signal to be transmitted via a wirenetwork, and accomplishes simple management for a wireless user anddynamic allocation of wireless channel.

Access point gateway (referred as APGW) 15 is mainly used to realizethree layer encapsulation for data of wireless local area networkterminal (i.e, encapsulating the Ethernet data package after APconversion into IP package) and de-encapsulation, and to transmit dataof wireless local area network terminal to packet data service node PDSN14, or to forward data transmitted from packed data service node PDSN 14to wireless local area network terminal.

The interface between packet control function node 12 and packet dataservice node 14 and the interface between wireless access point gateway15 and packet data service node 14 are all standard R-P interfaces.

The terminal of wireless local area network uses PPPoE dial form toaccess packet data service node 14, PPPoE dial access has negotiation intwo phrases: finding phrase and session phrase, in which the findingphrase is for finding the node wireless access point gateway 15 thatprovides service, and the session phrase is for realizing thenegotiation for point to point link between terminal and packet dataservice node 14.

As for a mobile station, in order to realize seamless handoff betweenCDMA 20001X system and wireless local area network system, it needs twoindependent air interfaces, which can connect to CDMA 20001X system andcan also connect to wireless local area network, and it has function ofindependent handoff between two systems, for example, when mobilestation detects that signal of wireless local area network fades to acertain extent, or when it has detected no signal of wireless local areanetwork, it performs access call to CDMA 20001X system; or after mobilestation reaches coverage area of wireless local area network, itautomatically connects to the wireless local area network. And at thesame time, mobile user should have ability to access two systems.

Because the coverage of current wireless local area network system onlylimits to hot pots, when a mobile station is far away from the accesspoint, error frame rate of data transmission will increase, and thetransmission rate will obviously decrease. At this time, the mobilestation needs to hand over automatically from wireless local areanetwork to CDMA 20001X system.

Furthermore, after a mobile station accesses the system via a wirelesslocal area network, it needs detect signal magnitude of wireless localarea network. If the signal of wireless local area network is weaker, orthe signal of wireless local area network can not be detected any more,the mobile station determines to hand over from wireless local areanetwork system to CDMA 20001X system according to a certain rule, suchas a pre-determined threshold of the signal magnitude, or thepre-determined rule for handoff.

From the description above, it can be know that the connection formbetween PCF 12 and PDSN 14 in CDMA 20001X system and the connection formbetween APGW 15 and PDSN 14 in WLAN system have function and networkingin common. PCF 12 and APGW 15 are all conversion interfaces betweenwireless and wire, the difference is only in the protocol of wirelessside process: when establishing PPP connection, PPP negotiation flowneeds to be accomplished, the protocol used in wireless local areanetwork system is PPPoE protocol, while the protocol used in CDMA 20001Xsystem is PPP protocol encapsulated by asynchronous HDLC; in the secondphrase of PPPoE—PPP session phrase, the protocol used is same as the PPPprotocol encapsulated by asynchronous HDLC. Furthermore, userinformation of them is also same in essence. Therefore, on the basis oforiginal function of PDSN 14, adding access of wireless local areanetwork users can support the access of PCF 12 and APGW 15 at the sametime. And at the same time, the PPP connection information of a user isstored in PDSN 14, which also provides possibility for seamlesslyhanding over a mobile station between WLAN system and CDMA 20001Xsystem.

FIG. 2 is an embodiment for accessing mobile station to wireless localarea network system and handing over from wireless local area networksystem to CDMA 20001X system, during handoff, packet data service nodedoes not change.

The step for accessing mobile station to wireless local area networksystem is described in the following. a connection is establishedbetween a mobile station and a wireless access point AP (step 201);after an air channel of wireless local area network is established, themobile station dials by using PPPoE form, and negotiation in PPPoEfinding phrase with a wireless access point gateway APGW is performed(step 202). After the wireless access point gateway permits the mobilestation to access, A11 registration request message is transmitted to apacket data service node, if the packet data service node receives theregistration request message, it returns A11 registration answer messageto the wireless access point gateway, after the wireless access pointgateway receives the answer message, a R-P connection between thewireless access point gateway and the packed data service node isestablished successfully (step 203). After the R-P connection betweenthe wireless access point gateway and the packet data service node isestablished successfully, between the mobile station and the packet dataservice node negotiation for point to point PPP link is performed.During establishment of a PPP connection, if the mobile station is asimple IP user, the packet data service node allocates a IP address tothe mobile station; if the mobile station is a mobile IP user, it needsperform further MIP registration (step 204). After the PPP link betweenthe mobile station and the packet data service node is establishedsuccessfully (for a mobile IP user, its registration of MIP is alsosuccessful), the packet data service node starts to provide datatransmission service for the mobile station (step 205).

Mobile station detects signals of the wireless local area networkcontinuously, when a signal of wireless local area network fades to apre-determined handoff threshold, the mobile station performs thefollowing steps for handing over from the wireless local area networksystem to CDMA 20001X system. The mobile station performs access call toCDMA 20001X system (step 206); after a base station permits the mobilestation to access, between a packet control function node and the packetdata service node a R-P connection is established (step 207). After theR-P connection between the packet control function node and the packetdata service node is established successfully, the packet data servicenode determines the user is a handoff user, that has established a linkconnection with the packet data service node, then data transmission isperformed between the mobile station and the packet data service nodevia the packet control function node (step 208), and finally the packetdata service node releases the R-P connection between the wirelessaccess point gateway and the packet data service node (step 209).

From the above steps, a process for accessing a mobile station to awireless local area network, and then handing over to the CDMA 20001Xsystem is accomplished. During the process of handoff, a method of firstestablishing a new link and then disconnecting original link is used.The packet data service node does not change during the handoff andre-negotiation of point to point PPP is not performed. Therefore,uninterrupted transmission of user data is ensured, and seamlessconnection is realized.

Also, after a mobile station accesses CDMA 20001X system, signals ofwireless local area network are continuously detected. If a signal of awireless local area network is detected, then the mobile station canhand over from CDMA 2000 1X system to the wireless local area networksystem according to a certain rule, such as a pre-determined thresholdof signal magnitude, or a pre-determined rule for handoff.

FIG. 3 is a handoff embodiment for accessing a mobile station to CDMA20001X system and handing over from CDMA 20001X system to wireless localarea network system, in which the packet data service node does notchange during handoff.

The steps for accessing mobile station to CDMA 2000 1X system aredescribed as the following. The mobile station performs dial call toCDMA 20001X system (step 301), and a R-P connection between a packetcontrol function node and a packet data service node is established(step 302). Then negotiation for point to point PPP link between themobile station and the packet data service node is performed (step 303);when the PPP link between the mobile station and the packet data servicenode is established successfully, the packet data service node providesdata transmission service for the mobile station (step 304).

After the mobile station detects a signal of a wireless local areanetwork, a connection is established between the mobile station and awireless access point (step 305). The mobile station decides whether itneeds handoff according to a certain rule. When the mobile stationdetermines to hand over from CDMA 20001X system to the wireless localarea network system, it performs PPPoE dial, and perform negotiation forPPPoE finding phrase with a wireless access point gateway (step 306).After the wireless access point gateway permits the mobile station toaccess, it transmits A11 registration request message to the packet dataservice node; if the packet data service node receives the registrationrequest message, it returns A11 registration answer message to thewireless access point gateway; after the wireless access point gatewayreceives the answer message, R-P connection is established successfully(step 307). Thereafter, the packet data service node determines themobile station is a handoff user, and data transmission is performedbetween the mobile station and the packet data service node via thewireless access point gateway (step 308), and at the same time, thepacket data service node releases the R-P connection between the packetcontrol function node and the packet data service node (step 309).

From the above steps, the process for accessing a mobile station to CDMA20001X system and handing over to wireless local area network system iscompleted.

During handoff, the method of first establishing a new link and thendisconnecting original link is also used; and during handoff,re-negotiation for point to point PPP is not performed, and transmissionof user data is not interrupted.

In a WLAN system and CDMA 20001X system, identification of a user isunique, so the user can use its NAI (Network Access Identifier) or MSID(Mobile Station Identifier) in CDMA 20001X system for authentication andaccounting under a WLAN mode.

In a conclusion, the method provided by the present invention forhanding over a mobile station between CDMA 20001X system and wirelesslocal area network system realizes seamless handoff between two systemsby using standard R-P interface and handoff function of packet dataservice node via wireless access point gateway APGW, and thereforeorganic combination of CDMA 20001X system and wireless local areanetwork system is realized. The handoff method of the present inventionalso adapts to a handoff between CDMA 20001X EV-DO, CDMA 20001X EV-DVand a wireless local area network system.

Lastly, it should be noted that the above embodiments are only forillustrating technical scheme of the present invention, without anylimitation. Although the present invention is described in detailsreference to the preferred embodiments, the ordinary person skilled inthe art should understand that the technical solution of the presentinvention can be modified or Substituted, without departing from thespirit and scope of the technical solution of the present invention, allof which should be covered in the scope of the following claims.

1. A method for handing over a mobile station from a wireless local areanetwork system to a CDMA 2000 system, comprising: step 1: when themobile station detects that a signal of the wireless local area networkis fading or has disappeared, determining to hand over the mobilestation from the wireless local area network to the CDMA 2000 system,the mobile performs step 2; step 2: initiating a call in the mobilestation in the CDMA 2000 system, after a base station permits the mobilestation to access, establishing R-P connection with a packet dataservice node by a packet control function node; step 3: after the packetdata service node determines the mobile station is a handoff user,establishing a data transmission channel in the CDMA 2000 for the mobilestation; and step 4: performing data transmission between the mobilestation and the packet data service node via the packet control functionnode, and disconnecting, by the packet data service node, the R-Pconnection established between the packet data service node and awireless access point gateway in wireless local area network system. 2.The method for handing over the mobile station from a wireless localarea network system to the CDMA 2000 system according to claim 1,wherein during handoff, the data transmission between the mobile stationand the packet data service node is forwarded via the wireless accesspoint gateway.
 3. The method for handing over the mobile station from awireless local area network system to the CDMA 2000 system according toclaim 1, wherein in the step 3, the packet data service node directlyuses PPP link information of original link without re-negotiation forpoint to point link.
 4. A method for handing over a mobile station froma CDMA 2000 system to a wireless local area network, comprising: step 1:after, the mobile station detecting a signal of the wireless local areanetwork, connecting to an access point in the wireless local areanetwork, and determining to hand over the mobile station from the CDMA2000 system to the wireless local area network system, the mobilestation performs step 2; step 2: performing dial connection to thewireless local area network system in the mobile station, andestablishing connection with a wireless access point gateway; step 3:after the wireless access point gateway permits the mobile station toaccess, establishing a R-P connection between the wireless access pointgateway and a packet data service node, data transmission is performedbetween the mobile station and the packet data service node via a packetcontrol function node; step 4: after the packet data service nodedetermines the mobile station is a handoff user, establishing a datatransmission channel to the wireless local area network for the mobilestation; and step 5: performing data transmission between the mobilestation and the packet data service node via the wireless access pointgateway, and disconnecting, by the packet data service node, the R-Pconnection established between the packet data service node and thepacket control function node in the CDMA2000 system.
 5. The method forhanding over the mobile station from the CDMA 2000 system to a wirelesslocal area network according to claim 4, wherein in the step 2, themobile station dials by using PPPoE form.
 6. The method for handing overthe mobile station from the CDMA 2000 system to a wireless local areanetwork according to claim 4, wherein the step 3 further comprises:after the wireless access point gateway permits the mobile station toaccess, transmitting A11 registration request message to the packet dataservice node, if the packet data service node receives the registrationrequest message, returning A11 registration answer message to thewireless access point gateway; whereby after the wireless access pointgateway receives the answer message, the R-P connection is establishedsuccessfully.
 7. The method for handing over the mobile station from theCDMA 2000 system to a wireless local area network according to claim 4,wherein in the step 4, the packet data service node directly uses PPPlink information of original link.
 8. The method for handing over themobile station from a wireless local area network system to the CDMA2000 system according to claim 1, wherein in the step 1, when a mobilestation detects that a signal of wireless local area network is fadingor has disappeared, if the determination is made not to hand over, themobile station continuously uses service provided by the originalwireless local area network system or disconnects the connection.
 9. Themethod for handing over the mobile station from the CDMA 2000 system toa wireless local area network according to claim 4, wherein in the step1, after detecting a signal of a wireless local area network in a mobilestation, connecting to an access point in the wireless local areanetwork, if the determination is made not to hand over, the mobilestation continuously uses service provided by the original CDMA 2000.